Dr. Javier Gonzalez-Sanchez javiergs@calpoly.edu www.javiergs.info o ffi ce: 14 -227 CSC 305 Individual Software Design and Development Lecture 10. Singleton

Previously

Scenario 1 3

Scenario 2 4

Scenario 3 5

Singleton

GoF Patterns 7

Singleton 8

Singleton class MainApp { public static void Main(String []a){ Singleton s1 = Singleton.getInstance(); Singleton s2 = Singleton.getInstance(); // Test for same instance if (s1 == s2){ // true - Objects are the same instance } } } 9

Singleton class Singleton{ private static Singleton _instance; private Singleton() {} public static Singleton getInstance(){ if (_instance == null){ _instance = new Singleton(); } return _instance; } } 10

Test Yourselves

Lab 12

Blueprint 13 M a in Dr a wAre a Dr a wAre a Listener Repository

Main 14

DrawArea 15

DrawAreaListener 16

Repository 17

Lab 18

Test Yourselves 19

Questions 20

Lab

Lab 22

Text • Can we draw the last 10 dots only? • Can we make darker the newest dot and light-gray (white) the oldest one? • Connect all the dots with a line, but instead of following the order in which they were clicked, connect them based on the shortest distance between each dot.

CSC 305 Individual Software Design and Development Javier Gonzalez-Sanchez, Ph.D. javiergs@calpoly.edu Summer 2024 Copyright. These slides can only be used as study material for the class CSC305 at Cal Poly. They cannot be distributed or used for another purpose.